On the National Asset Management Agency FAQ, part 2.3, my emphasis added:
Who will be footing the bill for the loans – the banks, the developers or the taxpayer?
NAMA acting for and on behalf of the taxpayer will not be paying book value for these assets, so on transfer of the assets the banks concerned will have to recognise losses on their books. Developers will be required to repay their loans and to the extent that they have made losses, they will have to recognise those – it will not be the function of NAMA to ‘go easy’ on them: NAMA’s mandate will be a commercial one. However, the stream of income from the assets and the proceeds from the eventual sale of the underlying asset will accrue to NAMA. The State will incur a loss only if the assets transferred to the State cannot over the long term repay the investment made by the State in their purchase from the banks. However, if NAMA make a loss over the long term, the Government intends that a levy should be applied to recoup the shortfall.
A levy on whom?
If it's a levy on the banks, any present-discounted amount of any putative shortfall will be much lower than the value of the shortfall, leaving the tax payer with the shortfall.
The small print giveth, and the large print taketh away folks.
Update: Karl Whelan makes the point much better than I could. Go read him instead.